1. Field of the Invention
The present invention relates to an antenna device which is capable of supporting multiple resonance frequencies.
2. Description of the Related Art
Conventionally, in order to multiple-resonate the resonance frequency of an antenna provided in communication equipment, there has been proposed an antenna including a radiation electrode and a dielectric block or an antenna device using a switch and a controlled voltage source.
For example, as a conventional technique using a dielectric block, Patent Document 1 discloses a high-efficiency composite antenna which is obtained by forming a radiation electrode into a molded resin article and then integrating the molded resin article and a dielectric block with an adhesive.
Also, as a conventional technique using a switch and a controlled voltage source, Patent Document 2 discloses an antenna device including a first radiation electrode, a second radiation electrode, and a switch which is interposed between the middle part of the first radiation electrode and the base end part of the second radiation electrode and electrically connects or disconnects the second radiation electrode to/from the first radiation electrode.